Pressure sensitive adhesives

ABSTRACT

A pressure sensitive adhesive is formed from a composition comprising mono-functional unsaturated acrylate ester monomer, essentially saturated tackifying resin polymer dissolved in the acrylate ester, non-crystallizing elastomeric material also dissolved in the acrylate ester, and an initiator responsive to ultraviolet light or other penetrating radiation such as electron beam, gamma or X-ray radiation. The composition is cured by subjection to ultraviolet light or other radiation, which causes the initiator to induce polymerization of both the acrylate ester and the non-crystallizing elastomeric material, apparently with co-polymerization therebetween.

This application is a continuation-in-part of my copending applicationSer. No. 873,869 filed Jan. 31, 1978, now abandoned, on "PressureSensitive Adhesive".

BACKGROUND OF THE INVENTION

This invention relates to improved pressure sensitive adhesives, and tocompositions and processes for forming such adhesives.

The most common methods of producing pressure sensitive adhesivesutilize compositions in which natural or synthetic rubber and atackifying resin are dissolved in a highly volatile solvent, with thesolvent ultimately being evaporated from the composition to leave thedissolved substances in place on a substrate. Such a process has thedisadvantage of requiring high thermal energy input for evaporating thesolvent, and introducing air pollution and fire hazard problems as aresult of emission of and the necessity to control the solvent vapors.In some instances, acrylic resin emulsions have been utilized in lieu ofthe solvent solutions, with resultant elimination of the fire hazard,but without overcoming the high thermal energy input requirementsbecause of a necessity for evaporating water from the emulsions. Otherprocesses employed in making pressure sensitive adhesives have utilizedhot melt compositions, but here again a great deal of energy is requiredfor heating the melt.

More recently, development work has been done with ultravioletpolymerization systems, employing compositions which are liquid at roomtemperature and are essentially solvent free, and will polymerize to apermanently tacky pressure sensitive film upon exposure to ultravioletlight. Other processes have employed different types of radiation, suchas for example electron beam radiation for causing polymerization of thepressure sensitive film. One patent stressing electron beam curing isU.S. Pat. No. 3,897,295, in which the composition subjected to theelectron beam includes an acrylate monomer selected from a particularspecified group, and a homo polymer or co-polymer of a substance orsubstances selected from the same group. The polymer is dissolved in themonomer, and the monomer is ultimately polymerized to bind the adhesivefilm together. This patent states that a thickener such as neoprene maybe added to the composition, as may other additives.

In some types of compounds in which acrylate monomers have beenemployed, such as for example in printing inks and the like, there havebeen intermixed with the acrylates a photo-initiator material which isadapted to respond to ultraviolet radiation in a manner inducingpolymerization of the acrylate to a hardened and cured form.

SUMMARY OF THE INVENTION

The present invention provides unique pressure sensitive adhesives whichcan be made without the necessity for high thermal input, and withoutemission of volatile solvent vapors into the atmosphere, and in anextremely simple and straight-forward manner resulting in a lower costof production than with most conventional processes. At the same time,however, the resultant product may have extremely effective adhesivecharacteristics, and those characteristics can be varied controllably byaltering proportions of the different ingredients used in thecomposition.

To achieve these results, the pressure sensitive adhesive of the presentinvention is formed from a composition which includes a monofunctionalunsaturated acrylate ester monomer, or mixture of such acrylate estermonomers, as a primary solvent of the composition, with there beingdissolved in the acrylate a thermoplastic tackifying resin polymer, ormixture of such polymers, and one or more natural or syntheticelastomeric materials of a non-crystallizing type. In conjunction withthese substituents, the composition also includes a free radicalgenerating initiator material which can respond to ultraviolet light,and which when subjected to such ultraviolet light will act as aphoto-initiator to induce polymerization of both the acrylate ester andthe non-crystallizing elastomer. This initiator will also inducepolymerization of the ester and elastomer when subjected to other typesof radiation, other than ultraviolet, such as electron beam radiation,or gamma or X-ray radiation. It is thought that the polymerizationincludes co-polymerization or cross linking between the acrylate esterand the elastomer, to produce a film or matrix throughout the ultimateadhesive layer which is extremely effective in maintaining the integrityof the layer and resisting its rupture under load forces, while at thesame time allowing flexibility of the cured adhesive in correspondencewith flexure of a substrate to which the adhesive layer may be secured.

Since the acrylate ester monomer which initially functions as a solventis reactive in the composition and ultimately polymerizes to act as afilm forming agent or matrix in the final adhesive, the solvent is notemitted as a volatile flammable vapor, and does not produce the adverseeffects accompanying use of such volatile solvents. While it iscontemplated that a limited amount of volatile solvent may, if desired,be utilized in conjunction with the other ingredients, it is preferredthat no such volatile solvent be employed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

To discuss the individual components of the adhesive forming compositionin detail, and with reference first to the acrylate monomer, whichfunctions as a reactive solvent in the composition, it is contemplatedbroadly that this ingredient of the composition may be anymonofunctional unsaturated acrylate ester monomer, or mixture of suchmonomers, whether aliphatic or cyclic, and if cyclic may be aromaticwith a six membered ring or rings, or have other numbers of members inits ring or rings. It is currently thought preferable that themonofunctional acrylate ester be a cyclic acrylate with a five memberedring. The optimum acrylate monomer thus far utilized istetrahydrofurfuryl acrylate, a cyclic five member monomer sold byDaubert Chemical Co. under the trade designation "Melcril 4079". Thestructural formula for this presently preferred acrylate is: ##STR1##

Within the broad category of monofunctional unsaturated acrylate estermonomers, it is in most instances desirable that the acrylate monomer bea substance or mixture of substances selected from the group consistingof ethyl acrylate, 2-ethyl hexyl acrylate, hydroxypropyl acrylate, 2,3dibromopropyl acrylate, n-propyl acrylate, butyl acrylate, iso-propylacrylate, n-decyl acrylate, iso-decyl acrylate, nonyl acrylate,iso-nonyl acrylate, benzyl acrylate (e.g. the product sold by DaubertChemical Co. as "Melcril 4085"), tetrahydrofurfuryl acrylate (e.g. theproduct sold by Daubert Chemical Co. as "Melcril 4079"),phenylcellosolve acrylate (also known as phenoxyethyl acrylate) (e.g.the product sold by Ware Chemical Co. as "Chemlink 160"), octylacrylate, iso-octyl acrylate, hydroxyethyl acrylate, ethyleneglycolacrylate phthalate (e.g. the product sold by Daubert Chemical Co. as"Melcril 4083"), butoxyethyl acrylate, ethoxyethyl acrylate, cyclohexylacrylate, lauryl acrylate, and isobornyl acrylate (e.g. "IBOA" of Rohm &Haas Co.).

The second principal ingredient of the composition is the tackifyingresin polymer, which may be any appropriately tacky essentiallysaturated thermoplastic tackifying resin polymer or polymers soluble inthe acrylate ester monomer or monomers used therewith. The tackifyingresin in its dissolved state is in sub-micron size within and uniformlydispersed throughout the acrylate or acrylates as a solvent. When theacrylate is ultimately polymerized to a continuous film form, thetackifying resinous polymer, still uniformly dispersed throughout thematrix, acts by reason of its molecular weight and tackiness to wet anysubstrate of higher surface energy than that inherent in the dissolvedparticles. The resinous polymer is selected to have a glass transitiontemperature low enough to give the polymer the desired tackiness andwetting characteristics.

Best results are achieved when the tackifying resin is a substance ormixture of substances selected from the group consisting of esters ofrosin, hydrogenated esters of rosin, modified rosin esters, esters ofpolymerized rosin, esters of hydrogenated rosin, hydrocarbon resin,linear homo polymers of alpha-methyl styrene, alpha-pinene terpenehydrocarbon resin, aromatic modified C-5 hydrocarbon resin, vinyltoluenealpha methyl styrene co-polymer resins, beta-pinene terpene resins,polycyclic hydrocarbon resins and technical hydroabietyl alcohol.

Certain specific commercially available materials falling within thisgeneral category of preferred tackifying resins are:

methyl esters of rosin, as sold by Hercules, Inc. under the trademark"Abalyn"

hydrogenated methyl esters of rosin, sold by Hercules, Inc. as"Hercolyn"

technical hydroabietyl alcohol, sold by Hercules, Inc. as "Abitol"

modified rosin ester, sold by Hercules, Inc. as "Cellolyn 104"

glycerol ester of pale wood rosin, sold by Hercules, Inc. as "Ester Gum8L"

diethyleneglycol ester of rosin, sold by Hercules, Inc. as "Flexalyn"

pentaerythritol ester of modified rosin, sold by Hercules, Inc. as"Pentalyn C"

pentaerythritol ester of rosin, sold by Hercules, Inc. as "Pentalyn A"

pentaerythritol ester of highly stabilized rosin, sold by Hercules, Inc.as "Foral 85"

resinous terpene polybasic acid, sold by Hercules, Inc. as "Petrex Acid"

ethylene glycol ester of polymerized rosins, sold by Hercules, Inc. as"Poly-pale Ester 1"

diethyleneglycol ester of polymerized rosin, sold by Hercules, Inc. as"Poly-pale Ester 2"

glycerol ester of polymerized rosin, sold by Hercules, Inc. as"Poly-pale Ester 10"

ethylene glycol ester of hydrogenated rosin, sold by Hercules, Inc. as"Staybelite Ester 1"

diethylene glycol ester of hydrogenated rosin, sold by Hercules, Inc. as"Staybelite Ester 2"

triethylene glycol ester of hydrogenated rosin, sold by Hercules, Inc.as "Staybelite Ester 3"

glycerol ester of hydrogenated rosin, sold by Hercules, Inc. as"Staybelite Ester 5"

mixed ester of hydrogenated rosin, sold by Hercules, Inc. as "StaybeliteEster 101"

aromatic modified C-5 hydrocarbon resin, sold by Exxon Chemical Co. as"Escorez 1511"

linear homopolymer of alpha-methyl styrene, sold by Amoco Chemical Corp.as "Amoco Resin 18"

alpha-pinene terpene hydrocarbon resin, sold by Hercules, Inc. as"Piccolyte A-100"

vinyltoluene-alpha methyl styrene co-polymer resin, sold by Hercules,Inc. as "Piccotex 75"

beta-pinene terpene resin, sold by Hercules, Inc. as "Piccolyte S-100"

polycyclic hydrocarbon resin, sold by Exxon Chemical Co. as "Escorez5280"

The third primary ingredient of the composition, that is, the elastomer,may broadly be any natural or synthetic elastomer or mixture ofelastomers which are soluble in the acrylate ester monomer or monomersof the composition, and which are of a non-crystallizing amorphouscharacter. It is found that elastomers which can crystallize, such asfor example polychloroprene (neoprene), are not desirable for use in thepresent compositions. For best results, it is currently felt preferablethat the elastomer employed in my compositions be a substance or mixtureof substances selected from the group consisting of the followingmaterials:

thermoplastic polyurethane, such as, for example, "Estane 5716" of B. F.Goodrich Co.

polyvinyl butyral, such as "Butvar 76" of Monsanto Polymers &Petrochemicals Co.

chlorosulfonated polyethylene, such as "Hypalon" of E. I. DuPont deNemours & Co.

butadiene-acrylonitrile co-polymer, such as "Hycar 1432" of B. F.Goodrich Chemical Co.

radial block styrene-butadiene-styrene co-polymer, such as "Solprene411" of Phillips Chemical Co.

lineal block styrene-butadiene co-polymer, such as "Solprene 1205" ofPhillips Chemical Co.

lineal block styrene-butadiene-styrene co-polymer, such as "Kraton 1102"of Shell Chemical Co.

styrene-isoprene-styrene lineal block co-polymer, such as "Kraton 1107"of Shell Chemical Co.

styrene-ethylene-butylene-styrene lineal block co-polymer, such as"Kraton G" of Shell Chemical Co.

stereo-specific styrene-butadiene co-polymer, such as "Stereon 700" ofFirestone Synthetic Rubber & Latex Co.

stereo-specific polybutadiene rubber, such as "Diene 55 NFA" ofFirestone Synthetic Rubber & Latex Co.

liquid synthetic polyisoprene, such as "Isolene 40" of Hardman, Inc.

de-polymerized natural rubber, such as "DPR-40" of Hardman, Inc.

carboxy terminated butadiene-acrylonitrile co-polymer, such as "Hycar1300×8" of B. F. Goodrich Chemical Co.

carboxy terminated butadiene-acrylonitrile co-polymer with randomcarboxyl groups on the chain, such as "Hycar 1300×9" of B. F. GoodrichChemical Co.

vinyl terminated butadiene-acrylonitrile co-polymer, such as "Hycar1300×14" of B. F. Goodrich Chemical Co.

amine terminated butadiene-acrylonitrile co-polymer, such as "Hycar1300×16" of B. F. Goodrich Chemical Co.

carboxy terminated liquid polybutadiene, such as "Butarez CTL, type I orII" of Phillips Chemical Co.

non-functional liquid polybutadiene, such as "Butarez NF" of PhillipsChemical Co.

hydroxy terminated liquid polybutadiene, such as "Butarez HTS" ofPhillips Chemical Co.

polyester resin, such as "Vitel PE-200" of The Goodyear Tire and RubberCo.

vinyl toluene resin, such as "Pliolite VT" of The Goodyear Tire andRubber Co.

high vinyl 1,2 polybutadiene, such as "Ricon 150" of Colorado ChemicalSpecialties, Inc.

high vinyl 1,2 polybutadiene styrene copolymer, such as "Ricon 100" ofColorado Chemical Specialties, Inc.

The fourth principal ingredient of the composition is the free radicalemitting initiator, which is a substance adapted to be excited whensubjected to penetrating radiation, such as ultraviolet light within awavelength range of between about 1800 and 4000 Angstroms and desirablybetween about 3500 and 3600 Angstroms. This initiator is also excitableby other types of penetrating radiation, such as electron beam, gamma orX-ray radiation. When excited by any of these types of radiation, theinitiator emits free radicals moving rapidly within the composition andacting to induce polymerization of both the monofunctional acrylate andthe elastomer, and, it is thought, to induce co-polymerization orcross-linking of these substances to form an overall continuous matrixof optimum integrity. The free radicals emitted by the initiator strikethe acrylate monomer and elastomer molecules and break them apart attheir double bonds, to thereby facilitate polymerization andcross-linking through the initially unsaturated points at which thosedouble bonds occurred.

It is also believed that the polymerization and cross-linking of thesubstances in the composition may be enhanced by the chain scissionaction of the ultraviolet or other radiation on any ethylenic typechains in the substances, which after scission present sites for theaction produced by the free radicals.

Any initiator capable of functioning in this manner may be employed.Desirably, the initiator is a substance or substances selected from thegroup consisting of all phenones and substituted phenones, preferablybenzophenone, diethoxyacetophenone, p-bromoacetophenone, and benzoinether.

The four ingredients thus far discussed are preferably present in thecomposition in the following proportions, by weight:

100 parts monofunctional unsaturated acrylate ester monomer

50 to 250 parts tackifying resin polymer

4 to 150 parts non-crystallizing elastomeric material

1 to 6 parts initiator

In addition to the four primary constituents, the composition mayinclude also any of various different types of additives for giving tothe composition or adhesive desired characteristics, or for preventingdegradation thereof, or for any other purpose. For example, it ishelpful to introduce into the composition during the initial mixingprocess an appropriate solvent-free anti-foam agent, such as the productsold by Mallinckrodt Chemical Co. as "BYK-O". The anti-foam agent may beutilized in a proportion of 0.1 to 6 parts by weight of the solvent-freeanti-foam agent to 100 parts of the acrylate ester.

The composition may also include a plasticizing oil or greasefunctioning as a softening agent for the elastomeric component, andacting to enhance the tackiness of the film, as well as functioning asan oxygen shield for the surface of the wet, unpolymerized, adhesivefilm by a slight degree of blooming to the surface, thereby reducingoxygen inhibition of the polymerization of the acrylate monomer andelastomer. Any of the known oils or greases usable for this purpose maybe employed, desirably selected from the group consisting of aromaticprocess oil (e.g. "Petroflux LV" of Witco Chemical Co.), naphthenicprocess oil (e.g. "Cyclolube 1114" of Witco Chemical Co.),paraffinic-naphthenic process oil (e.g. "Cyclolube 1413" of WitcoChemical Co. or "Stanplas LPO" or "Stanplas MPO" of Golden Bear RefiningCo.), lithium grease (as sold for example by Lubriko Master LubricantsCo.), petrolatum, purified mineral oil, and white mineral oil. Theplasticizing oil or grease is preferably present in the amount ofbetween about 0.2 and 20 parts by weight for 100 parts of the acrylateester monomer.

To controllably alter the stiffness or shear strength of the finishedadhesive, along with the degree of tackiness desired, and the rate ofincrease in peel strength of an applied carrier film, as well as therate of polymerization desired in the finished adhesive, I may add tothe composition a polyfunctional acrylate ester monomer, which by virtueof its polyfunctionality will act to increase the cross-linkingpolymerization within the ultimate adhesive. This component should bepresent in an amount between about 0.1 and 25 parts by weight for each100 parts by weight of the monofunctional acrylate monomer. Thepolyfunctional acrylate ester monomer may be any substance fallingwithin that broad category, but preferably is a substance or mixture ofsubstances selected from the group consisting oftrimethylolpropanepropoxylate triacrylate, trimethylolpropanetriacrylate (e.g. "Chemlink 31" of Ware Chemical Co.), 1,6 hexanedioldiacrylate, triethylene glycol diacrylate (e.g. "Chemlink 32" of WareChemical Co.), neopentylglycol diacrylate (e.g. "Chemlink 127" of WareChemical Co.), pentaerythritolglycol diacrylate, pentaerythritoltriacrylate (e.g. "Chemlink 41" of Ware Chemical Co.),tetraethyleneglycol diacrylate (e.g. "Chemlink 25" of Ware ChemicalCo.), melamine acrylate, and diethyleneglycol diacrylate.

An anti-oxidant may also be included in the composition, to avoiddegradation of the adhesive by oxidation thereof, and in most instancesis preferably a substance or mixture of substances selected from thegroup consisting of tetrabis methylene 3-(3¹ -5¹ -di-tertbutyl-4¹-hydroxyphenyl) proprionate methane (e.g. "Irganox 1010" of Ciba-GeigyChemical Co.),1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene(e.g. "Antioxidant 330" of Ethyl Corp.), and 2(4-hydroxy-3,5-t-butylanilino) 4,6-bis(n-octylthio) 1,3,5-triazine (e.g. "Irganox 565" ofCiba-Geigy Chemical Co.). The anti-oxidant is preferably present in aproportion of about 0.5 to 1.5 parts by weight for each 100 parts of theelastomer.

If the proportions of the four primary ingredients and tackifying agentsselected do not result in the solution viscosity desired for aparticular method of application of the adhesive to a particularsubstrate, a thickening substance may be added in an appropriate amount,such as a silica aero-gel (e.g. "Cab-O-Sil" of Cabot Chemical Co.),asbestos fibers (e.g. "Resin Grade Asbestos" of Union Carbide Corp.), orthe like, or a surface active agent such as "Fluorad FC 431" ofMinnesota Mining & Manufacturing Co. may be added in minor proportions(typically about 0.12 parts or more by weight per 100 parts of themonofunctional acrylate ester) to improve substrate or carrier wetting.

Because of the number of possible compounding ingredients, theproperties of pressure sensitive adhesives prepared according to thisinvention can be varied to satisfy most foreseeable requirements fortack, peel strength, shear strength and solvent media resistance, onwhatever combination of carrier surface and substrate may beencountered. Variations of these properties of a given adhesivecomposition can also be obtained by varying the processing conditions,that is, by coating and curing either on the intended carrier surface oron the intended protective release sheet if one is to be used, by curingin air or an inert atmosphere, by varying the intensity of theultraviolet light or other radiation utilized in polymerization, etc.

The adhesive in its uncured state may be coated onto an appropriatesubstrate in any convenient manner, as by knife coating, spraying, orthe like, and is then cured by subjection to radiation of any of thediscussed types. Presently preferred are ultraviolet light where minimumcost of equipment is a factor, and electron beam radiation where maximumthroughput of product is desired. The radiation may be applied to theadhesive either by moving the radiation source while the product isstationary, or by moving the coated substrate past the radiation source,in either event the movement being at a rate causing the proper amountof total radiation energy to impinge upon each unit area of the product.The quantity of radiation to which the adhesive is subjected, whether itbe ultraviolet or electron beam radiation or another type, is such as toattain a full cure of the particular composition employed, typicallybetween about 1 and 10 megrads, and in most cases not over 5 megrads.The substrate may be a flexible tape of Mylar or other material, or be arigid part or other structure of any type.

The following typical examples are given of certain specific adhesiveswhich have been made in accordance with the invention.

EXAMPLE 1

A composition was formed utilizing the following ingredients in theindicated proportions by weight:

    ______________________________________                                        Material                 Parts by Weight                                      ______________________________________                                        tetrahydrofurfuryl acrylate (monofunctional                                   acrylate monomer)        100.00                                               pentaerythritrol ester of highly stabilized                                   rosin (Foral 85) (tackifying resin)                                                                    107.420                                              carboxy terminated butadiene-nitrile copolymer                                (Hycar 1300X9) (elastomer)                                                                             7.511                                                lineal block styrene-butadiene-styrene                                        copolymer (Kraton 1102) (elastomer)                                                                    25.000                                               diethoxyacetophenone (photo-initiator)                                                                 5.808                                                anti-foam agent (BYK-O)  2.5                                                  trimethylpropane triacrylate (polyfunctional                                  acrylate monomer)        1.000                                                anti-oxidant (Irganox 1010)                                                                            .134                                                 paraffinic naphthenic blend plasticizing oil                                  (Stanplas LPO)           5.000                                                ______________________________________                                    

The tetrahydrofurfuryl acrylate was first mixed with the anti-foamagent, following which the other ingredients with the exception of thephoto-initiator were mixed in. Finally, the photo-initiator was mixedinto the composition. The mixture was applied to a substrate of aluminumwhich was 0.007 inches thick, and which had been thoroughly cleaned withan appropriate solvent and then dried. The composition was applied tothe aluminum as a film having a thickness of 0.002 inches, and aftercoating was subjected to ultraviolet radiation at a wavelength ofapproximately 3600 Angstroms, with the coating exposed to air during theultraviolet radiation step. The film was moved at a rate of 50 feet perminute past and perpendicular to three 200 watt per inch ultravioletlamps, to excite the photo-initiator, which in turn causedpolymerization of the acrylate monomers and elastomers, apparently withcross-linking between the acrylates and elastomers as previouslydiscussed.

The resulting adhesive functioned very effectively as a pressuresensitive adhesive for securing the aluminum substrate to a chromeplated surface, with moderate tack. When tested for adhesion between thesolvent cleaned aluminum substrate and chrome plated brass bar stock,the adhesive evidenced an initial 90° peel strength of 6 to 7 pounds perinch, and a rolling ball tack of 11/2 inches.

EXAMPLE 2

There was applied to a flexible Mylar film substrate a compositionidentical with that referred to in Example 1, except for the addition of2.1 parts by weight of hydroabietyl alcohol for each 100 parts of theoverall composition of Example 1. The Mylar was 0.001 inches inthickness, and a coating of 0.001 inches of the adhesive composition wasapplied thereto. The coated Mylar was advanced at a rate of 50 feet perminute past and perpendicular to three 200 watts per inch ultravioletlamps, to excite the photo-initiator and polymerize the acrylate monomerand elastomeric components of the composition. The adhesive evidenced avery high tack, and appeared very well adapted for general purpose use.When tested for adhesion between the coated Mylar strip and paintedsteel, the pressure sensitive adhesive coating showed an initial 90°peel strength of 4 pounds per inch, and a rolling ball tack of 1/4 inch.

EXAMPLE 3

A very effective water-white adhesive for a transparent film carrier wasproduced, utilizing a composition consisting of the followingingredients:

    ______________________________________                                        Material                Parts by Weight                                       ______________________________________                                        n-butyl acrylate (monofunctional                                              acrylate monomer)       100.000                                               tetrahydrofurfuryl acrylate (monofunctional                                   acrylate monomer)       25.000                                                polycyclic hydrocarbon resin (Escorez 5280)                                   (tackifying resin)      83.334                                                hydroabietyl alcohol (Abitol) (tackifying                                     resin)                  43.491                                                carboxy terminated butadiene nitrile                                          (Hycar 1300 × 9) (elastomer)                                                                    5.166                                                 linear block styrene-butadiene-styrene                                        copolymer (Kraton 1102) (elastomer)                                                                   41.666                                                diethoxyacetophenone (photo-initiator)                                                                7.250                                                 antifoam agent (BYK-O)  .834                                                  anti-oxidant (Irganox 1010)                                                                           .209                                                  paraffinic naphthenic blend plasticizing oil                                  (Stanplas LPO)          5.166                                                 ______________________________________                                    

This composition was coated to a thickness of 0.001 inches on acellophane film of 0.001 inches thickness, and was polymerized bymovement at a rate of 120 feet per minute past and perpendicular tothree 200 watt per inch ultraviolet lamps. There was no visiblediscoloration of the unpigmented cellophane, and a slight improvement inesthetic appeal. The coating showed an initial 90° peel strength of 4pounds per inch, and a rolling ball tack of 1/8 inch.

EXAMPLE 4

A flexible corona treated Mylar film substrate 1/2 mil thick was coatedwith a composition formed of the following ingredients in theproportions indicated by weight:

    ______________________________________                                        Material                Parts by Weight                                       ______________________________________                                        n-butyl acrylate (monofunctional                                              acrylate monomer)       39.7                                                  trimethylolpropanetriacrylate                                                 (polyfunctional acrylate monomer)                                                                     4.4                                                   lineal block styrene-butadiene-styrene                                        copolymer (Kraton 1102) elastomer                                                                     20.0                                                  anti-oxidant (Irganox 1010)                                                                           .1                                                    hydrogenated rosin ester (Foral 85)                                           tackifying resin        85.3                                                  paraffinic naphthenic blend plasticizing                                      oil (Stanplas LPO)      4.0                                                   carboxy terminated butadiene-nitrile                                          copolymer (Hycar 1300 × 9)                                                                      5.96                                                  diethoxyactophenone (initiator)                                                                       2.3                                                   ______________________________________                                    

All ingredients of this composition except the initiator were firstmixed together, following which the initiator was blended in. After thecomposition had been coated onto the Mylar, it was subjected to electronbeam radiation by progressive movement of the coated tape past a sourceof such radiation, with the total dose applied to each point on thecoating being 3 megrads. This radiation cured the compositioncompletely. Under test, the coating evidenced a 4 pound per inch 180°peel strength-Mylar to painted steel.

The same composition cured in the same way but with only 2 megrads ofelectron beam radiation was also completely cured and evidenced as gooda peel test as the sample subjected to 3 megrads. A composition whichwas identical except for deletion of the initiator showed only 2 poundsper inch 180° peel strength and 85% cohesive failure when subjected to 3megrads of electron beam radiation, and required 6 megrads of suchradiation for a complete cure.

ADDITIONAL EXAMPLES

Other examples of adhesives which have been produced in accordance withthe invention and cured by ultraviolet light are set forth in thefollowing charts, in which the ingredients are identified by numberswhose significance is set forth in a listing following the charts:

    ______________________________________                                                  Example 5 Ex. 6   Ex. 7  Ex. 8 Ex. 9                                ______________________________________                                        Ingredient 1                                                                            100.00                                                              Ingredient 2        100.00                                                    Ingredient 3                100.00                                            Ingredient 4                       100.00                                                                              100.00                               Ingredient 5        34.79                                                     Ingredient 6                                                                            60.00                                                               Ingredient 7                143.4  300.00                                                                              100.00                               Ingredient 8                                                                  Ingredient 9        66.7                                                      Ingredient 10                                                                           50.00     33.3    33.45                                             Ingredient 11                                                                 Ingredient 12                                                                 Ingredient 13                                                                 Ingredient 14                                                                 Ingredient 15                                                                 Ingredient 16       4.1     10.0   200.0 100.0                                Ingredient 17                                                                 Ingredient 18                                                                 Ingredient 19                                                                 Ingredient 20                                                                 Ingredient 21                                                                 Ingredient 22                                                                 Ingredient 23                                                                           5.80      5.80    4.75   5.80  2.00                                 Ingredient 24       4.1     6.67                                              Ingredient 25                                                                 Ingredient 26                                                                           2.0                                                                 Ingredient 27                                                                           .25       .167    .167                                              ______________________________________                                                  Example 10                                                                              Ex. 11  Ex. 12 Ex. 13                                                                              Ex. 14                               ______________________________________                                        Ingredient 1                                                                            100.00                                                              Ingredient 2                       100.00                                     Ingredient 3        100.00  100.00       100.00                               Ingredient 4                                                                  Ingredient 5                                                                  Ingredient 6                                                                  Ingredient 7                                                                            143.4     107.5          106.4                                      Ingredient 8                161.2                                             Ingredient 9                                                                  Ingredient 10                                                                           33.37     25.00   24.94  24.7                                       Ingredient 11                                                                 Ingredient 12                                                                 Ingredient 13                                                                 Ingredient 14                                                                 Ingredient 15                                                                 Ingredient 16                                                                           10.0      7.51    7.51   7.44                                       Ingredient 17                                                                 Ingredient 18                                                                 Ingredient 19                            25.00                                Ingredient 20                                                                 Ingredient 21                                                                 Ingredient 22                                                                 Ingredient 23                                                                           5.84      5.80    5.80   5.75  5.75                                 Ingredient 24                                                                           6.67      5.00    5.00   4.95                                       Ingredient 25                                                                           1.00      1.00    1.00   1.00  1.00                                 Ingredient 26                                                                 Ingredient 27                                                                           .166      .125    .125   .125                                       ______________________________________                                                  Example 15                                                                              Ex. 16  Ex. 17 Ex. 18                                                                              Ex. 19                               ______________________________________                                        Ingredient 1                                                                  Ingredient 2                                                                  Ingredient 3                                                                            100.00    100.00  79.41  79.41 79.41                                Ingredient 4                                                                  Ingredient 5                                                                  Ingredient 6                                                                  Ingredient 7                                                                            106.4     105.0   85.30  85.30 85.30                                Ingredient 8                                                                  Ingredient 9                                                                  Ingredient 10                                                                 Ingredient 11                      19.85                                      Ingredient 12                            19.85                                Ingredient 13       25.0                                                      Ingredient 14                                                                 Ingredient 15                                                                 Ingredient 16                                                                           7.43              5.96   5.96  5.96                                 Ingredient 17                                                                 Ingredient 18                                                                 Ingredient 19                                                                 Ingredient 20                                                                           25.00                                                               Ingredient 21               19.85                                             Ingredient 22                                                                 Ingredient 23                                                                           5.74      5.75    4.61   4.61  4.61                                 Ingredient 24                                                                           4.96              3.97   3.97  3.97                                 Ingredient 25                                                                           1.00      1.00    .79    .79   .79                                  Ingredient 26                                                                 Ingredient 27                                                                 ______________________________________                                                  Example 20                                                                              Ex. 21  Ex. 22 Ex. 23                                                                              Ex. 24                               ______________________________________                                        Ingredient 1                                                                  Ingredient 2                       39.7                                       Ingredient 3                                                                            39.64     39.64   39.64  39.7  19.85                                Ingredient 4                                                                  Ingredient 5                                                                  Ingredient 6                                                                  Ingredient 7                                                                            42.65     42.65   42.65  84.45 21.33                                Ingredient 8                                                                  Ingredient 9                                                                  Ingredient 10                                                                 Ingredient 11                                                                 Ingredient 12                                                                 Ingredient 13                                                                 Ingredient 14       2.5                                                       Ingredient 15                            4.97                                 Ingredient 16                                                                           2.98      2.98    2.98         1.49                                 Ingredient 17                      25.57                                      Ingredient 18               9.93                                              Ingredient 19                                                                 Ingredient 20                                                                 Ingredient 21                                                                 Ingredient 22                                                                           2.5                                                                 Ingredient 23                                                                           2.31      2.31    2.31   4.65  1.16                                 Ingredient 24                                                                           1.99      1.99    1.99   3.93  .99                                  Ingredient 25                                                                           .40       .40     .40    .794  .20                                  Ingredient 26                                                                 Ingredient 27                                                                 ______________________________________                                    

In the above charts, the proportions of the various ingredients in eachexample are given in terms of parts by weight. To simplify the chartsthe ingredients are identified in the charts by number, with the numbershaving the following significance:

Acrylates

Ingredient 1--benzyl acrylate

Ingredient 2--n-butyl acrylate

Ingredient 3--tetrahydrofurfuryl acrylate

Ingredient 4--phenylcellosolve acrylate

Tackifying Resins

Ingredient 5--technical hydroabietyl alcohol

Ingredient 6--glycerol ester of pale wood rosin

Ingredient 7--pentaerythritol ester of highly stabilized rosin

Ingredient 8--vinyl toluene-alpha methyl styrene resin

Ingredient 9--polycyclic hydrocarbon resin

Elastomers

Ingredient 10--linear block styrene-butadiene-styrene

Ingredient 11--radial block styrene-butadiene-styrene

Ingredient 12---linear block styrene butadiene

Ingredient 13--chlorosulfonated polyethylene

Ingredient 14--stereo-specific styrene-butadiene

Ingredient 15--hydroxy terminated liquid polybutadiene

Ingredient 16--carboxy terminated butadiene-nitrile

Ingredient 17--vinyl terminated butadiene-nitrile

Ingredient 18--amine terminated butadiene-nitrile

Ingredient 19--thermoplastic polyurethane

Ingredient 20--polyvinyl butyral

Ingredient 21--vinyl toluene resin

Ingredient 22--polychloroprene

Photo-initiator

Ingredient 23--diethoxyacetophenone

Plasticizing oil

Ingredient 24--aromatic process oil

Polyfunctional acrylates

Ingredient 25--trimethylolpropane triacrylate

Ingredient 26--penterythritolglycol triacrylate

Anti-oxidant

Ingredient 27--tetrabis methylene 3-(3¹ -5¹ -di-tertbutyl-4¹-hydroxyphenyl) proprionate methane

While certain specific embodiments of the present invention have beendisclosed as typical, the invention is of course not limited to theseparticular forms, but rather is applicable broadly to all suchvariations as fall within the scope of the appended claims.

I claim:
 1. A composition for forming a pressure sensitive adhesive,comprising by weight:about 100 parts monofunctional unsaturated acrylateester monomer; between about 50 and 250 parts essentially saturatedthermoplastic tackifying resin polymer dissolved in said acrylate estermonomer; between about 4 and 150 parts non-crystallizing elastomericblock copolymer dissolved in said acrylate ester monomer; and initiatorresponsive to radiation to induce copolymerization of the acrylate estermonomer and the non-crystallizing elastomeric block copolymer.
 2. Acomposition as recited in claim 1, in which said acrylate ester monomeris a monomer or mixture of monomers selected from the group consistingof ethyl acrylate, 2-ethylhexyl acrylate, hydroxypropyl acrylate, 2,3dibromopropyl acrylate, n-propyl acrylate, butyl acrylate, iso-propylacrylate, n-decyl acrylate, iso-decyl acrylate, nonyl acrylate,iso-nonyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate,phenylcellosolve acrylate (phenoxyethyl acrylate), octyl acrylate,iso-octyl acrylate, hydroxyethyl acrylate, ethyleneglycol acrylatephthalate, butoxyethyl acrylate, ethoxyethyl acrylate, cyclohexylacrylate, lauryl acrylate, and isobornyl acrylate.
 3. A composition asrecited in claim 1, in which said tackifying resin polymer is a polymeror mixture of polymers selected from the group consisting of esters ofrosin, hydrogenated esters of rosin, modified rosin esters, esters ofpolymerized rosin, esters of hydrogenated rosin, hydrocarbon resin,linear homo polymers of alpha-methyl styrene, alphapinene terpenehydrocarbon resin, aromatic modified C-5 hydrocarbon resin, vinyltoluenealpha methyl styrene co-polymer resins, beta-pinene terpene resins,polycyclic hydrocarbon resins, and technical hydroabietyl alcohol.
 4. Acomposition as recited in claim 1, in which said initiator is asubstance or mixture of substances selected from the group consisting ofall phenones and substituted phenones.
 5. A composition as recited inclaim 1, including polyfunctional acrylate ester monomer intermixed withthe other ingredients.
 6. A composition as recited in claim 1, includingpolyfunctional acrylate ester monomer intermixed with the otheringredients, and being a substance or substances selected from the groupconsisting of trimethylolpropanepropoxylate triacrylate,trimethylolpropane triacrylate, 1,6 hexanediol diacrylate,triethyleneglycol diacrylate, neopentylglycol diacrylate,pentaerythritolglycol diacrylate, pentaerythritol triacrylate,tetraethyleneglycol diacrylate, melamine acrylate, and diethyleneglycoldiacrylate.
 7. A composition as recited in claim 1, in which saidinitiator is responsive to ultraviolet light to induce polymerization ofthe acrylate ester monomer and the non-crystallizing elastomericmaterial.
 8. A composition as recited in claim 1, in which saidinitiator is responsive to electron beam radiation to inducepolymerization of the acrylate ester monomer and the non-crystallizingelastomeric material.
 9. A composition as recited in claim 1, includingan anti-foaming agent.
 10. A composition as recited in claim 1,including an anti-oxidant.
 11. A composition as recited in claim 1,including an oil intermixed with the other ingredients.
 12. Acomposition for forming a pressure sensitive adhesive, comprising byweight:about 100 parts tetrahydrofurfuryl acrylate monomer; betweenabout 50 and 250 parts essentially saturated tackifying resin polymerdissolved in said tetrahydrofurfuryl acrylate monomer; between about 4and 150 parts non-crystallizing elastomeric block copolymer havingstyrene blocks and dissolved in said tetrahydrofurfuryl acrylatemonomer; and between about 1 and 6 parts initiator responsive toradiation to induce copolymerization of the tetrahydrofurfuryl acrylatemonomer and the non-crystallizing elastomeric block copolymer.
 13. Theprocess of forming a pressure sensitive adhesive thatcomprises:providing a composition including, by weight, about 100 partsmono-functional unsaturated acrylate ester monomer, between about 50 and250 parts essentially saturated thermoplastic tackifying resin polymerdissolved in said acrylate ester monomer, between about 4 and 150 partsnon-crystallizing elastomeric block copolymer dissolved in said acrylateester monomer, and initiator responsive to radiation; subjecting saidcomposition to radiation to which said initiator is responsive; andinducing copolymerization of said acrylate ester monomer and saidnon-crystallizing elastomeric block copolymer by said initiator.
 14. Theprocess as recited in claim 13, in which said acrylate ester monomer isa substance or substances selected from the group consisting of ethylacrylate, 2-ethyl hexyl acrylate, hydroxypropyl acrylate, 2,3dibromopropyl acrylate, n-propyl acrylate, butyl acrylate, iso-propylacrylate, n-decyl acrylate, iso-decyl acrylate, nonyl acrylate,iso-nonyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate,phenylcellosolve acrylate (phenoxyethyl acrylate), octyl acrylate,iso-octyl acrylate, hydroxethyl acrylate, ethyleneglycol acrylatephthalate, butoxyethyl acrylate, ethoxyethyl acrylate, cyclohexylacrylate, lauryl acrylate, and isobornyl acrylate.
 15. The process asrecited in claim 13, in which said tackifying resin polymer is asubstance or substances selected from the group consisting of esters ofrosin, hydrogenated esters of rosin, modified rosin esters, esters ofpolymerized rosin, esters of hydrogenated rosin, hydrocarbon resin,linear homo polymers of alpha-methyl styrene, alpha-pinene terpenehydrocarbon resin, aromatic modified C-5 hydrocarbon resin, vinyltoluenealpha methyl styrene co-polymer resins, beta-pinene terpene resins,polycyclic hydrocarbon resins and technical hydroabietyl alcohol. 16.The process as recited in claim 13, in which said non-crystallizingelastomeric block copolymer is a substance or substances selected fromthe group consisting of radial block styrene-butadiene-styreneco-polymer, lineal block styrene-butadiene co-polymer; lineal blockstyrene-butadiene-styrene co-polymer, styrene-isoprene-styrene linealblock co-polymer, and styrene-ethylene-butylene-styrene lineal blockco-polymer.
 17. The process as recited in claim 13, in which saidinitiator is a substance or substances selected from the groupconsisting of all phenones and substituted phenones.
 18. The process asrecited in claim 13, in which said radiation is ultraviolet light. 19.The process as recited in claim 13, in which said radiation is electronbeam radiation.
 20. A pressure sensitive adhesive formed by the methodrecited in claim
 13. 21. A pressure sensitive adhesive formed by themethod recited in claim
 16. 22. A pressure sensitive adhesive formed bythe method recited in claim
 14. 23. The process of forming a pressuresensitive adhesive that comprises:providing a composition including, byweight, 100 parts tetrahydrofurfuryl acrylate ester monomer, betweenabout 50 and 250 parts essentially saturated tackifying resin polymerdissolved in said tetrahydrofurfuryl acrylate ester monomer, betweenabout 4 and 150 parts non-crystallizing elastomeric block copolymerdissolved in said tetrahydrofurfuryl acrylate ester monomer, andinitiator responsive to radiation to emit free radicals; subjecting saidcomposition to radiation to which said initiator is responsive; andinducing copolymerization of said tetrahydrofurfuryl acrylate estermonomer and said non-crystallizing elastomeric block copolymer by saidinitiator.
 24. A pressure sensitive adhesive made by the process ofclaim
 23. 25. A composition as recited in claim 1, in which saidnon-crystallizing elastomeric block copolymer is a substance or mixtureof substances selected from the group consisting of radial blockstyrene-butadiene-styrene co-polymer, lineal block styrene-butadieneco-polymer, lineal block styrene-butadiene-styrene co-polymer,styrene-isoprene-styrene lineal block co-polymer, andstyrene-ethylene-butylene-styrene lineal block co-polymer.
 26. Acomposition as recited in claim 1, in which said acrylate ester monomeris a substance or substances selected from the group consisting of ethylacrylate, 2-ethyl hexyl acrylate, hydroxypropyl acrylate, 2,3dibromopropyl acrylate, n-propyl acrylate, butyl acrylate, iso-propylacrylate, n-decyl acrylate, iso-decyl acrylate, nonyl acrylate,iso-nonyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate,phenylcellosolve acrylate (phenoxyethyl acrylate), octyl acrylate,iso-octyl acrylate, hydroxyethyl acrylate, ethyleneglycol acrylatephthalate, butoxyethyl acrylate, ethoxyethyl acrylate, cyclohexylacrylate, lauryl acrylate, and isobornyl acrylate; said tackifying resinbeing a substance or substances selected from the group consisting ofesters of rosin, hydrogenated esters of rosin, modified rosin esters,esters of polymerized rosin, esters of hydrogenated rosin, hydrocarbonresin, linear homo polymers of alpha-methyl styrene, alphapinene terpenehydrocarbon resin, aromatic modified C-5 hydrocarbon resin, vinyltoluenealpha methyl styrene copolymer resins, beta-pinene terpene resins,polycyclic hydrocarbon resins and technical hydroabietyl alcohol; saidnon-crystallizing elastomeric block copolymer being a substance orsubstances selected from the group consisting of radial blockstyrene-butadiene-styrene copolymer, lineal block styrene-butadienecopolymer, lineal block styrene-butadiene-styrene copolymer,styrene-isoprene-styrene lineal block copolymer andstyrene-ethylene-butylene-styrene lineal block copolymer; and saidinitiator being a substance or substances selected from the groupconsisting of benzophenone, diethoxyacetophenone, p-bromoacetophenone,and benzoin ether.
 27. A composition as recited in claim 26, includingpolyfunctional acrylate ester monomer intermixed with the otheringredients.
 28. A composition as recited in claim 27, including ananti-foaming agent, an oil, and an anti-oxidant intermixed with theother ingredients.
 29. A composition for forming a pressure sensitiveadhesive, comprising:monofunctional unsaturated acrylate ester monomer;essentially saturated thermoplastic tackifying resin polymer dissolvedin said acrylate ester monomer; non-crystallizing elastomeric blockcopolymer dissolved in said acrylate ester monomer; and initiatorresponsive to radiation to induce copolymerization of the acrylate estermonomer and the non-crystallizing elastomeric block copolymer.
 30. Theprocess of forming a pressure sensitive adhesive that comprisessubjecting the composition of claim 29 to radiation to which saidinitiator is responsive, and inducing copolymerization of said acrylateester monomer and said block copolymer by said initiator.
 31. A pressuresensitive adhesive formed by the process of claim
 30. 32. A compositionfor forming a pressure sensitive adhesive, comprising:monofunctionalunsaturated acrylate ester monomer; essentially saturated thermoplastictackifying resin polymer dissolved in said acrylate ester monomer;chlorosulfonated polyethylene dissolved in said acrylate ester monomer;and initiator responsive to radiation to induce copolymerization of theacrylate ester monomer and the chlorosulfonated polyethylene.
 33. Acomposition for forming a pressure sensitive adhesive,comprising:monofunctional unsaturated acrylate ester monomer;essentially saturated thermoplastic tackifying resin polymer dissolvedin said acrylate ester monomer; carboxy terminatedbutadiene-acrylonitrile copolymer dissolved in said acrylate estermonomer; and initiator responsive to radiation to inducecopolymerization of the acrylate ester monomer and the carboxyterminated butadiene-acrylonitrile copolymer.
 34. A composition asrecited in claim 33, in which said carboxy terminatedbutadiene-acrylonitrile copolymer has random carboxyl groups on thechain.
 35. A composition for forming a pressure sensitive adhesive,comprising:monofunctional unsaturated acrylate ester monomer;essentially saturated thermoplastic tackifying resin polymer dissolvedin said acrylate ester monomer; vinyl terminated butadiene-acrylonitrilecopolymer dissolved in said acrylate ester monomer; and initiatorresponsive to radiation to induce copolymerization of the acrylate estermonomer and the vinyl terminated butadiene-acrylonitrile copolymer. 36.The process of forming a pressure sensitive adhesive that comprisessubjecting the composition of claim 32 to radiation to which saidinitiator is responsive; and inducing copolymerization of said acrylateester monomer and said chlorosulfonated polyethylene by said initiator.37. The process of forming a pressure sensitive adhesive that comprisessubjecting the composition of claim 33 to radiation to which saidinitiator is responsive; and inducing copolymerization of said acrylateester monomer and said carboxy terminated butadiene-acrylonitrilecopolymer.
 38. The process of forming a pressure sensitive adhesive thatcomprises subjecting the composition of claim 35 to radiation to whichsaid initiator is responsive; and inducing copolymerization of saidacrylate ester monomer and said vinyl terminated butadiene-acrylonitrilecopolymer.
 39. A pressure sensitive adhesive formed by the process ofclaim
 36. 40. A pressure sensitive adhesive formed by the process ofclaim
 37. 41. A pressure sensitive adhesive formed by the process ofclaim 38.